1. Field of the Invention
The present invention is coaxial cable connectors and more particularly to such a coaxial cable connector that fits a series of coaxial cables having one same specification and different wire outer diameters.
2. Description of the Related Art
In current television market, cable TV is the mainstream. Cable TV signal is transmitted to a television of a subscriber through a coaxial cable. Coaxial cable is not limited to cable TV application, it can also be used in any of a variety of other fields for signal transmission. For two-way high-frequency transmission, a coaxial cable is extended from an outdoor place to the inside of a house and then connected to a TV or TV splitter through a coaxial cable connector. This coaxial cable connector is adapted for connecting a coaxial cable to a mating connector at the TV or TV splitter.
To fit different signal transmission quality requirements, the braided outer conductor of a coaxial cable can have a standard, tri-shield or quad-shield design. In consequence, the wire outer diameter is relatively changed. Further, a coaxial cable further comprises an aluminum foil surrounding the insulation spacer within the braided outer conductor to provide a shielding effect.
Many coaxial cable connectors are commercially available for assembly with one of a series of coaxial cables having different wire outer diameters. FIG. 1 illustrates a cable end connector A fastened to one end of a coaxial cable B. This cable end connector A consists of a screw nut A1, a plastic body shell A2, an inner tube A3 and a metal barrel A4.
The screw nut A1 is disposed at the front side, having an inner thread for threading onto a mating connector. The plastic body shell A2 is connected to the screw nut A1. A gasket ring A21 is set in between the plastic body shell A2 and the screw nut A1. The inner tube A3 is inserted into the inside of the plastic body shell A2. The metal barrel A4 is sleeved onto one end of the plastic body shell A2 adjacent to the coaxial cable B.
During installation, as shown in FIG. 1, the protective plastic covering of the coaxial cable B is properly stripped off, and then the center conductor B1 of the coaxial cable B is inserted through the metal barrel A4 into the inner tube A3, and then a crimping tool is operated to crimp the cable end connector A, forcing the metal barrel A4 along the plastic body shell A2 toward the screw nut A1, thereby finishing the installation, as shown in FIG. 1A. At this time, a sufficient space is left between the outer edge of the barbed end portion A31 of the inner tube A3 and the inner end edge A23 of the plastic body shell A2 for receiving one of a series of coaxial cables having one same specification and different wire outer diameters. By means of the elastically deformable property of a specially configured packing portion A22 of the plastic body shell A2, a coaxial cable B having a different wire outer diameter can be tightly sealed in this cable end connector A. With respect to the details of this cable end connector, please refer to U.S. Pat. No. 6,848,939, entitled “Coaxial cable connector with integral grip bushing for cables of varying thickness”.
However, when the aforesaid cable end connector A is assembled with a coaxial cable B, the plastic body shell A2 is partially exposed to the weather (see FIG. 1A) and will become aged and oxidized soon. Therefore, the application of this design of cable end connector is limited. In actual application, this design of cable end connector still has drawbacks as follows:
1. The plastic body shell A2 is partially exposed to the outside between the screw nut A1 and the metal barrel A4. When the cable end connector A is used outdoor, the plastic body shell A2 will become aged and oxidized soon under the effect of the sun, rain and wind, and rainwater may leak in between the cable end connector A and the coaxial cable B, affecting signal transmission stability and quality. If a metal body shell is used to substitute for the plastic body shell A2, the crimping operation during installation of the cable end connector will become difficult. Therefore, this design of cable end connector is not well invited in the market.2. A long distance is left between the aluminum foil insertion hole A32 on the left end of the inner tube A3 and the left orifice A41 of the metal barrel A4. This distance is approximately equal to the length of the bare aluminum foil B31 of the coaxial cable B (or even longer), as shown in FIG. 1. Thus, it is difficult to insert the insulation spacer B2 and aluminum foil B3 of the coaxial cable B into the cable end connector A, and the insulation spacer B2 and aluminum foil B3 of the coaxial cable B may be damaged during insertion, affecting signal transmission quality and stability. To avoid this problem, it is necessary to shorten the distance between the aluminum foil insertion hole A32 on the left end of the inner tube A3 and the left orifice A41 of the metal barrel A4 to about ⅔ of the length of the bare aluminum foil B31 of the coaxial cable B. In this case, the inner diameter of the inner end edge A23 of the plastic body shell A2 will be reduced due to engagement between of the clamping portion A22 of the plastic body shell A2 and the beveled clamping surface A42 of the metal barrel A4, interfering with the insertion of the coaxial cable B.
FIG. 2 illustrates another structure of connector D according to the prior art, which consists of a screw nut D1, an inner tube D2, a body shell D3, a barrel D4 and a plastic bushing D5. Unlike the prior art design shown in FIG. 1, the plastic bushing D5 is mounted in the body shell D3 and the barrel D4 and kept from sight.
The screw nut D1 is connected with one end of the inner tube D2 for the passing of the center conductor B1 of the coaxial cable B. The body shell D3 surrounds the inner tube D2. The inner tube D2 has a barbed portion D21 disposed at one end thereof and extending out of one end of the clamping portion D31 of the body shell D3. The barrel D4 is sleeved onto the clamping portion D31 of the body shell D3. The plastic bushing D5 is set in the barrel D4.
A large space is left between the outer edge D211 of the barbed portion D21 of the body inner tube D2 and an inner end edge D51 of the plastic bushing D5 for receiving a different thickness of braided outer conductor of a coaxial cable of one same specification. By means of the elastically deformable property of the plastic bushing D5, the connector fits cables of varying thickness.
In the aforesaid cable end connector D, the body shell D3 is a metal member, and a crimping tool must be used to crimp the clamping portion D31 of the body shell D3 and the barrel D4 during installation of the cable end connector D. Because the crimping distance D32 has a certain length, much crimping pressure must be applied to the crimping tool to move he barrel D4 relative to the clamping portion D31 subject to the crimping distance D32. Thus, much effort is necessary to complete the crimping operation. Further, a long distance is left between the aluminum foil insertion hole D2 on the left end of the inner tube D2 and the left orifice D41 of the metal barrel D4. This distance is greater than the length of the bare aluminum foil B31 of the coaxial cable B. Thus, it is difficult to insert the insulation spacer B2 and aluminum foil B3 of the coaxial cable B into the cable end connector D, and the insulation spacer B2 and aluminum foil B3 of the coaxial cable B may be damaged during insertion. During a high-frequency two-way signal transmission operation, this aluminum foil damage causes an increase in the reflective loss, affecting signal transmission quality and stability. To avoid this problem, it is necessary to shorten the distance between the aluminum foil insertion hole D2 on the left end of the inner tube D2 and the left orifice D41 of the metal barrel D4 to about ⅔ of the length of the bare aluminum foil B31 of the coaxial cable B. In this case, the inner diameter of the inner end edge D51 of the plastic bushing D5 will be reduced due to engagement between of the clamping portion D52 of the plastic bushing D5 and the beveled clamping surface D33 of the body shell D3, interfering with the insertion of the coaxial cable B.